Once again, it is becoming clear that host immune defenses are dependent not only specific immunological mechanisms, but also upon the milieu in which these processes take place: an internal micro-environment modified by many non-specific factors. The overall objectives of this proposal are to study the manner in which the brain, intermediate between the environment and the immune response, can modulate the ability of the organism to invoke adequate defenses against various pathogens. The objectives of the proposal are to study the immunological response to infectious and non-infectious agents in rodents subjected to acute or chronic stress. The neural control of the stress-induced modulation of the immune response will be analyzed by examining the patterining of humoral and immunological changes, to these stressors consequent to the ablation of specific hypothalamic nuclei.